Fuel burner control system



March 19, 1940. w. J. McGbLDRlCK 2,194,245

FUEL BURNER CONTROL SYSTEM Filed July 13, 1939 ihmmtor William J. M Golrlrick.

Patented Mar. 19, 1940 UNITED STATES PATENT OFFICE 2,194,245 FUEL BURNER CONTROL SYSTEM Delaware Application July 13, 1939, Serial No. 284,223

10 Claims.

This invention is directed to a simplified control system for fuel burners in which a pair of electrical timers are utilized to actuate the fuel feeding device and also to provide the proper safety features in case of flame or ignition failure.

It is an object of the present invention to provide such a system wherein the two timers maintain a predetermined relationship to each other so long as the system is operating normally, but on a flame or ignition failure this predetermined relationship is destroyed and the system goes out on safety.

A further object of the invention is to provide a system of the above type in which thermal timers are'used, one being energized by a main controlling switch and the other being energized by a thermostat responding to combustion.

These and other objects will readily become apparent to those skilled in the art as the following specification is read in the light of the accompanying drawing in which the single figure shows a diagrammatic representation of my invention.

The main control device for the system of my invention is in the form of a room thermostat indicated generally at The thermostat takes the form of a coiled bimetallic element l2 which is fixed at one end and at its free end carries a contact blade I3 which cooperates with a stationary contact H. The thermostat is so arranged that on a decrease in temperature the bimetal coil will move the blade l3 into engagement with the stationary contact I4 and on an increase in temperature these contacts will be separated.

Mounted on supports 6 and I1 respectively are a pair of bimetal timers l6 and I9. The bimetal timer at its free end pivotally carries a lever 20 which has depending from its lower side a block 2|. When both of the timers are at substantially the same temperature the block 2| rests on the upper end of the bimetal timer IS in the manner shown in the dmwing. Closely associated with the bimetal timer 3 is an electric heating element 23 for the purpose of heating the timer to cause it to warp toward the left. A second electric heating element 25 is associated with the bimetal timer l9 and when energized causes this timer to warp toward the left, as seen in the drawing.

Spring contact blade 26 is fixedly supported at one end to the bracket 21 and has attached thereto at the lower side a supporting member 28. The blade 26 is normally biased toward the lever 20 and its position is therefore determined by this lever. On its upper side the contact blade 26 carries an electric contact 30 which cooperates with a second electric contact 3| carnied by the spring contact blade 32. The spring 6 contact blade 32 is fixedly secured to the bracket 33 and is biased in a direction toward the lever 26 so that when the lever 26 is supported as shown in the drawing, the contacts 30 and 3| are in engagement. 1o

Slidable within a support is a. reset member generally indicated at 36. This reset member comprises a plate 31 carrying three reset fingers 38, 39, and 40 each of which has an insulated tip. The stem 4| is slidably received in the support 35 and carries a knob 42 whereby the reset member may be vertically moved within the support. The purpose and function of this reset member will appear in a description of the operation of the present invention. I

Pivotally mounted at 50 is an arm 5| carrying a mercury switch generally indicated at 52 and comprising a glass tube 53 and a globule of mercury 54. The mercury switch is provided with a pair of electrodes 55 and 56 which the mercury 54 is adapted to alternately bridge and unbridge. A connecting arm 56 is pivotally connected to the arm 5| and to the bimetal timer l8 in such a manner that as the bimetal timer |8 warps to the left the arm 5| will be rotated in a direction to cause the mercury 54 to bridge the electrodes 55 and 56 of the mercury switch 52.

The present control system is provided with the usual electrical fuel delivery means which in this case is in the form of an oil burner motor 60. Ignition device 6| is supplied for the purpose of igniting the fuel delivered by the motor 60. i

Indicated generally at 63 is a combustion responsive switch which comprises a switch arm 40 64 and stationary contact 65. It will be understood that this is merely a diagrammatic representation and that the switch arm 64 is to be actuated by some means responsive to combustion which may be located within the furnace to respond to radiant heat of the flame or which may be mounted in the stack to respond to the temperature of the products of combustion. A slip friction mechanism is inserted between the combustion responsive means and the switch arm 64 in order that the switch may be actuated in response to a change in the temperature to which the combustion responsive means responds and not in accordance with any predetermined temperature. Such devices are of course old and. well known in the art.

In considering the operation of the present control system, let it be assumed that the room thermostat H is satisfied and that the switch arm |3 has been out of engagement with the contact M for a suflicient length of time for the bimetal timers l8 and i9 to have returned to their cold positions and for the combustion responsive contacts 64 and 65 to have moved into engagement. It will be noted that when the switch arm 64 is in engagement with contact 65, a circuit is completed from the line wire l0 through conductors H, 12, switch arm 64, contact 65, conductor I3, protective resistance 14, and conductor 15 back to the other line wire 16. The above circuit shunts out the electric heater 25 thus permitting the bimetal timer l9 to remain in its cold position. The movement of the bimetal timer l8 to cold position 'moves the mercury switch 52 to its open circuit position thereby deenergizing the motor 60 and ignition means 6|.

Asa result of the above condition, the temperature will begin to drop at the room thermostat II and eventually the bimetallic element I2 will move switch arm |3 into engagement with the stationary contact M. This closes a circuit from the line wire 10, conductor 18, bimetallicv element l2, switch arm l3, contact |4, conductor 19, contact blade 32, contacts 3| and 30, contact blade 26, conductors and 8|, electric heater 23, conductor 82, protective resistance 83, and conductor 84 back to the line wire 16. The result of this circuit is to energize the electric heater 23 causing the bimetallic timer to warp toward the left. -As the timer |8 warps towards the left,

it tilts the glass tube 53 until the mercury 54 bridges the electrodes 55 and 56. This sets up a parallel circuit from the conductor 80 to conductor 85, electrode 56, mercury 54, electrode 55, conductors 86 and 8], burner motor 60, and conductor 88 back to the line wire I6. The ignition means 6| is simultaneously energized by means of conductors 89 and which place the ignition means in parallel with the motor 60. The energization of motor 60 and ignition means 6| normally establishes combustion which will cause the combustion responsive device 63 to move the switch arm 64 out of engagement with the stationary contact 65. This breaks the shunt circuit about the electrical heater 25 which will now be energized by means of the following circuit: line wire 10, conductors H and 9|, electric heating element 25, conductor 92, protective resistance 14, and conductor 15 back to the other line wire 16.

As a result of the energization of the electric heater 25, the bimetallic element l9 will warp toward the left. The relationship of the bimetallic timers I8 and 9 and the supporting block 2| is such that the bimetallic timer l8 may warp toward the left to close the mercury switch 52 resulting in the energization of the burner motor 60 and ignition means 6| to produce combustion thereby causing the combustion responsive device 63 to open the contacts 64 and 65 energizing the heater 25 before the block 2| has moved to the left far enough to drop off the end of the bimetallic timer |9. After the heater 25 has been energized, the bimetallic timer l9 moves to the left along with the block 2| so that normally the lever 20 remains in the horizontal position thereby holding the switch contacts 30 and 3| closed.

This is the normal running position of the system.

After the temperature at the thermostat M has been sufficiently raised the bimetallic element l2 will cause the switch arm 03 to separate from the stationary contact Ml thereby deenergizing the burner motor 65, ignition means ill and the electric heater 23. Bimetal timer l8 will therefore begin to cool and move toward the right. Combustion having ceased to exist within the furnace, the switch arm 64 will move into engagement with the contact 65 thereby shunting the electric heater 25 with the result that the bimetal timer l9 will also cool and warp toward the right along with the timer I8 and the block 2| will continue to rest on the free end of the timer l9 and maintain the switch contacts 30 and 3| in closed position. Therefore during normal operation of the system the contacts 30 and 3| will remain closed at all times.

Let us assume now that the room thermostat H is calling for heat and has caused the switch arm |3 to engage the contact |4 thereby energizing the electric heater 23. As a result, the bimetallic timer 8 will warp toward the left and close the mercury switch 52 energizing the burner motor 60 and ignition means 6|. If for some reason combustion should not take place, the switch arm 64 would remain in engagement with the contact 65 thereby preventing energization of the electric heater 25. The bimetallic timer I8 would therefore remain stationary and after the timer |8 had warped to the left a predetermined amount the supporting block 2| for the lever 28 would drop off the end of the timer l9. The end of the lever 20 would then drop onto the arm 38 of the resetmember and the spring biased contact blade 26 would drop on the arm 38 while the arm 40 would prevent the contact blade 32 from following the contact blade 26. Contacts 30 and 3| would therefore be separated breaking the circuit to the motor 60, ignition means 6| and electric heater 23. The bimetallic timer l8 would then cool and tend to warp toward the right. The parts would remain in this position until the lever 20 has been reset upon the upper end of the timer l9 thereby closing the contacts 30 and 3|. This resetting operation is accomplished by means of the reset member 36 which is moved vertically upwardly by means of the knob 42. It will be noted that as the arms 38 and 39 reset the lever 20 and contact blade 26 to the positions shown in the drawing that the arm 40 will hold the contacts 30 and 3| separated until the reset 36 is released and then the contacts 30 and 3| will move into engagement only if the timers I8 and I9 are in such position that the supporting block 2| engages the free end of the timer l9. In other words, the reset member 36 provides a trip free reset action. The system is then capable of making another attempt at a normal start.

If the system should be running normally and a flame failure should occur, the combustion responsive device 63 would immediately respond and move the switch arm 64 into contact with the stationary contact 65. The result of this is to shunt the electric heater 25 causing the bimetal timer I9 to cool and warp toward the right. The electric heater 23 Will remain energized due to the fact that the room thermostat H is still calling for heat so that the timer I8 will hold the block 2| over toward the left and as the timer I9 continues to warp toward the right the block 2| will after a predetermined length of time drop off the end of the timer 19. This opens the switch contacts 30 and 3| which shuts down the system in the same manner as described in connection with the ignition failure. The system will remain in this condition until reset by means of the reset member 36 in the same manner as described above.

On power failure should the system be in running condition both of the electric heaters 23 and 25 will be deenergized and the timers will move together to their cold position where the system will be in condition for another normal start after the power has been resumed.

It will therefore be seen that I have provided a simplified form of oil burner control system wherein a pair of bimetal timers not only actuate the control switch for the burner motor and ignition means but also cooperate with the safety switch 30 and 3| to provide the proper features of safety in case of flame or ignition failure.

Other modifications of this invention may occur to those who are skilled in the art and I therefore wish it to be understood that I am to be limited only by the scope of the appended claims and not by the specific embodiment disclosed.

I claim as my invention:

1. A control system for fuel burners comprising in combination, a pair of timers, means energizing one of said timers, a fuel feeding device rendered operative by said one timer upon energization thereof and rendered inoperative again by a predetermined relative movement between said timers, and means energizing the other timer as a result of combustion to prevent said predetermined relative movement.

2. A control system for fuel burners comprising in combination, a pair of electrical timers, a main switch for energizing one of said timers, an electrical fuel feeding device, a circuit therefor, said one timer upon energization closing said circuit and upon continued movement relative to said other timer breaking said circuit again, and means responsive to combustion energizing said other timer causing it to move along with said one timer and maintain said circuit closed.

3. A control system for fuel burners comprising in combination, a pair of electrical timers, a main switch for energizing one of said timers, an electrical fuel feeding device, a circuit therefor, said one timer upon energization closing said circuit and upon continued movement relative to said other timer breaking said circuit again, electrical means for energizing said other timer, a switch closing a shunt circu t around said electrical means, and means responsive to combustion opening said last named switch whereby said other timer moves along with said one timer and maintains the circuit for said fuel feeding device closed.

4. A control system for fuel burners comprising in combination, an electrical fuel feeding device, a circuit therefor including a control switch and a biased open safety switch, a pair of timers, said timers holding said safety switch in closed position as long as they bear a substantially predetermined relation to each other, means energizing one of said timers to cause it to move and close said control switch for energizing said fuel feeding device, said timer upon continued movement being operative to destroy said predetermined relation, and means responsive to combustion energizing the other timer for movement in a direction to maintain said predetermined relation.

5. A control system for fuel burners comprising in combination, an electrical fuel feeding device, a circuit therefor including a control switch and a biased open safety switch, a pair of timers, said timers holding said safety switch in closed position as long as they bear a substantially predetermined relation to each other, means energizing one of said timers to cause it to move and close said control switch for energizing said fuel feeding device, said timer upon continued movement being operative to destroy said predetermined relation and trip said safety switch to open position, manual means for resetting said safety switch after said timers are in a condition to return to their predetermined relation, and means responsive to combustion energizing the other timer for maintaining said predetermined relation if it has not already been destroyed.

6. A control system for fuel burners comprising in combination, a pair of timers, means energizing one of said timers, a fuel feeding device .rendered operative by said one timer upon energization thereof and rendered inoperative again by a predetermined relative movement between said timers, and means energizing the other timer as a result of combustion to cause it to move in a direction to prevent said relative movement, said means deenergizing said other timer as a result of a subsequent failure of combustion to cause it to move in the opposite direction relative to said one timer and hence render said fuel feeding device inoperative.

'7. A control system for fuel burners comprising in combination, a pair of electrical timers, a main switch for energizing one of said timers, an electrical fuel feeding device, a circuit therefor, said one timer upon energization closing said circuit and upon continued movement relative to said other timer breaking said circuit again, and means responsive to combustion energizing said other timer causing it to move along with said one timer and maintain said circuit closed, said means on subsequent failure of combustion deenergizing said other timer causing it to reverse its movement relative said one timer and open said circuit.

8. A control system for fuel burners comprising in combination, an electrical fuel feeding device, a circuit therefor including a control switch and a biased open safety switch, a pair of timers, said timers holding said safety switch in closed position as long as they bear a substantially predetermined relation to each other, means energizing one of said timers to close said control switch for energizing said fuel feeding device, said timer upon continued movement being. operative to destroy said predetermined relation, and means responsive to combustion energizing the other timer for movement in a direction to maintain said predetermined relation, said last mentioned means on subsequent failure of combustion deenergizing said other timer causing it to reverse its movement and hence trip said safety switch to open position.

9. A control system for fuel burners comprising in combination, an electrical fuel feeding device, a circuit therefor, a pair of bimetal timers, a main switch, a heater energized by said main switch for heating one of said bimetal timers which upon initial movement closes said circuit and after a predetermined movement relative to the other of said timers reopens said circuit, a second heater, and means energizing said second heater in response to combustion I for causing said other timer to move in the same direction as said one timer thereby preventing said predetermined relative movement between them. 7

10. A control system for fuel burners comprising in combination, an electrical fuel feeding device, a circuit therefor, a pair of bimetal timers, a main switch, a heater energized by said main switch for heating one of said bimetal timers which upon initial movement closes said circuit and after a; predetermined movement relative to the other of said timers reopens said circuit, a second heater, and means energizing said second heater in response to combustion for causing said other timer to move in the same direction as said one timer thereby preventing said predetermined relative movement between them, said means on a subsequent failure of ignition deenergizing said second heater whereupon said other timer accomplishes said predetermined movement in the opposite direction thereby opening said circuit.

WILLIAM J. MCGOLDRICK. 

